Method of electrodepositing metals and apparatus therefor



Nov. 3, 1931. M. J. UDY 1,830,343

METHOD OF ELECTRODEPOSITING METALS AND APPARATUS THEREFOR Fild Nov. 5,1926 I II!!! II I IIIIIIIIII/l I I II I II III III III III! II I I I IIII FIG. I. FIG.2.

v INVENTOR.

@ ATTORNEYS.

' Patented Nov. 3, 193 1.

' mm J. may,

OF NIAGARA FALLS, NEW YORK mz'rnon or mmonnrosrme METALS AND arrmrusTHEREFOR Application filed November a, 1926. Serial m. 140,000.

This invention relates to an improvement in the art of electrodepositingmetals and more particularly to an improved method of, and apparatusfor, obtaining unlform current distribution over the article to beplated.

While my invention may be used to advantage in the electrodeposition ofany of the metals, it is of particular advantage in those caseswhere thebath has a poor throwing power, where a high cathode current density isrequired, and where therefore a uniform current distribution is of thegreatest importance. By poor throwin power is meant that when anirregularly shaped article is being plated, those portions farthest fromthe anode receive a very much lighter deposition of metal than theportions' closest to the anode, or may not receive any metal at alldepending on the. shape and size of the article p 20 and various otherfactors. Such conditions exist in the electrodeposition of chromium andfor this reason my invention 1s particularly suitable for electroplatingarticles with ticles of all sizes but its advantages are more pronouncedin the plating of articles. having relatively large surface areas suchas metal sheets and plates. My invention has for a principal object theobtention of uniform current distribution over the article to be platedand this is brought about by making the electrical connections betweenthe cathode current lead and the article to be plated by means of amultiplicity of point or line contacts.

The invention has for a further object the use of means for supportingand electrically connecting the article to be plated which permit of theplating of all the surface portions of the article; that is, not onlythose which are normally in contact with the plating bath, but alsothose which are normally shielded from the bath by such supporting andcurrent-conducting means as are commonly employed.

Y The accompanying drawings illustrate an embodiment of the invention.

Fig.1 is a view in elevation of a form of the invention applicable inplating sheets.

chromium; The method is applicable to a'r Fig. 2 is a cross-sectionalview taken on the line A-A of Fig 1.

In the drawings 10 is a copper or other suitable conductive metal stripor bar adapted to support a sheet or other article to be plated and toconnect the article to a suitable current lead not shown. The metalstrip 10 is provided with a serrated edge portlon 11. The alternateteeth are bent to'the right and left-respectively much in the samemanner as in setting a saw, with the result that the teeth are arrangedinto two parallel rows so inclined the one to the other as to form aV-shaped groove or recess between them. A serrated strip 10 is ressedagainst each edge 5 of the sheet to be plhted, referred to as 12 in thedrawings, v,so that the edge of the sheet will fit into the groove orrecessformed between the two rows of teeth. It will be observed that thesneet forms aline contact with a limited portion of each tooth orserration of the strip 10. A suflicient number of, points or lines ofcontact are provided to make it possible to pass the required currentthrough the article without the necessity of clamping or otherwisefastenin current leads to the sheet or other article to h plated.

A further advantage of the use of a multiplicity of point or linecontacts for electrically connecting the sheet to the appropriate 8current lead lies in the fact that all the surface portions, even thosesmall portions of the surface of the sheet or other article which restupon the serrated edge portion of the metal stri 10, receive a coatingof chromium.

The fact t at deposition of the plating metal takes place on theseapparently shielded portions of the article is contrary to what wouldordinarily be expected. It is advanced as a possible explanation that acertain amount of vibration is set up in the article during the platingoperation, particularly when operating under the high current densitycon-- .ditlons obtaining in electrodepositing chromium. On the otherhand, is may be that a slight creeping of theplating bath takes placebetween the article and the support and is sufficient toinsure that theentire point, edge, or other small area of contact between the articleand the support will be sufiiciently wet with of deposition of theplating bath to permit the plating metal thereon. However, the inventionis not dependent upon the correctness of the theories advanced and theyare not to be construed to limit the invention in any way.

proven satisfactory in securing plating completely enveloping sheets orother along the edg ing the plating operation. This shifting may e orsurface of the article durbe produced manually at will or periodicallyby mechanical means as desired. One form of means for producing periodicrelative movement between the sheet which is being plated and thecurrent-conductingmeans is shown more or less diagrammatically inFig. 1. This consists of cams 13 positioned in the plating bath so as tocontact with the opposite side edge portions of the sheet 12. These camsare connected through a suitable mechanlsm, not" shown, to rotate e1thercontinuously or periodically. Thereby causing the sheet to move backandforth along the current-conductor 10. When means for shifting thearticle back and forth along the conductor are used, it maybe desirableto omit such conductors from the side edge portions as shown in Fig. 1.Many forms of apparatus will readily suggest themselves as equivalent tothe cams13 for bringing about relative movement between the sheet andthe con ductor 10, and these are considered to be embraced within thepresent invention. In-

' stead of reciprocating the sheet the desired result may be obtained byreciprocating the conductor whichcontaots with the sheet. 7

While I have described with particularity one embodiment of myinvention, it is not to be understood therefrom that the invention isrestricted to such embodiment. Various modifications. may be. made bythose "skilled in the art without departing from the invention asdefined in the following claims.

What I claim is:

1. In electroplating apparatus for plating sheets, means for obtaininguniform deposition over the sheet to be plated, comprising a conductorhaving a multiplicity of relatively sharp projecting portions biased toengage the sheet and'form a'discontinuous contact area therewith. saidcontact being of a limted point or line character. 1

2. In electroplating apparatus, means for obtaining uniform depositionover the article to be plated, comprising a conductor having arelatively sharp serrated edge portion of sawtooth character adapted toengage the art cle and form a discontinuous contact areatherewith, saidcontact being of a limited point or line character. 3. In electroplatingapparatus for plating sheets, means for obtaining uniform depositionover the sheet to be plated, comprising a conductor having a relativelysharp serrated edge portion, said serrations bein biased to engage thesheet at a plurality 0 point or line contacts. I

I 4. In electroplating'apparatus for plating articles, means forobtaining uniform deposition over an article to beplated, comprising aconductor having a multiplicity of projections', said projections beingarranged in two adjacent rows inclined the one to the other so as toformbetween the outer extremities of the projections of the adjacentrows a reccss V-shaped in cross-section, 'ing adapted to receive an edgeportion of the article to be plated.

5. In electroplating apparatus, means for obtaining uniform depositionover the article to be plated, comprising a conductor having amultiplicity of projecting portions biased to-engagean article to beplated and form'a discontinuous contact area therewith, and meansadapted to produce relative movement between such article during theelectroplating operation.

6. In electroplating apparatus for plating sheets, means for obtaininguniform deposition over the article to be plated, comprisingcurrent-conducting means adapted to engage the exterior edge portionsonly of said article and to make limited relatively sharp contactcontact and thesurface of the said recess beadjacent to and at amultiplicity of points along such edge portions.

' 7. Process of obtaining uniform deposition of chromium on metalarticles which comprises forming a multiplicity of contacts .of limitedarea between the article and a conductor of electric current, passingcurrent between the article and an anode in a chromium plating bath, andcausing the said contacts to assume difierentpositions on the surface ofthe article while the deposition is conductor shaped to the peripheralcontour of an article to be plated, and adapted to make contact with anedge of said article, said conductorhaving a portion composed of amultiplicit of sharp projections adapted to make imme iate contact" withsaid article.

9. Process of obtaining uniform deposi-. tion of metal on metal articleswhich comprises forming a multiplicity of contacts of limited areabetween the article and a conductor of electric current, passing currentbetween the art! 1e and an anode in a plating bath, and positivelycausing the said contacts 'to assume difierent positions on the surfaceof the article while the place, so as to efiect deposition is takingplating on practically all portions of the said article.

10. An electro-plating apparatus of the character set forth in claim 5in which the" means adapted to produce relative movement between thearticle to be plated and the supporting contacts is of a reciprocatingcharac- 'ter.

MARVIN aturei

